In 2002 Democratic U.S. Senator Paul Wellstone of Minnesota, who was running for re-election, died in a plane crash just 11 days before the November 5 election. At the age of 74, Mondale replaced Wellstone on the ballot, at the urging of Wellstone’s relatives. This Senate seat was the one that Mondale himself had held, before resigning to become Vice President in 1977.
During his debate with the Republican nominee, former St. Paul Mayor Norm Coleman, Mondale emphasized his own experience in foreign affairs while painting Coleman as a finger-in-the-wind opportunist. “We’ve seen you shift around, Norman”, Mondale said, alluding to Coleman’s past as an anti-war college activist and, more recently, as a Democrat who had changed his party allegiance to the GOP while serving as mayor of St. Paul.
Mondale lost the election, finishing with 1,067,246 votes (47.34%) to Coleman’s 1,116,697 (49.53%) out of 2,254,639 votes cast, earning him the unique distinction of having lost a statewide election in all 50 states as the nominee of a major party (he lost the other 49 in the 1984 Presidential Election). Upon conceding defeat, Mondale stated: “At the end of what will be my last campaign, I want to say to Minnesota, you always treated me well, you always listened to me.”
In 2004 Mondale became co-chairman of the Constitution Project’s bipartisan Right to Counsel Committee. He endorsed Senator Hillary Clinton (D-NY) for the Presidency of the United States and supported her campaign for the White House in 2008. On June 3, 2008, following the final primary contests, Mondale switched his endorsement to Senator Barack Obama (D-Ill.), who had clinched the nomination the previous evening.
Following the U.S. presidential election of 2004 and the mid‑term elections of 2006, Mondale is seen talking with Al Franken about the possibility of the latter running for Norm Coleman’s U.S. Senate seat in 2008 in the documentary Al Franken: God Spoke. In the film, Mondale encourages Franken to run, but cautions him, saying that Coleman’s allies and the Republican Party were going to look for anything they could use against him. Franken ultimately ran and won the 2008 Senate election by 312 votes after the election results had been contested in court by Coleman until June 30, 2009. Mondale and Senator Amy Klobuchar stood with Franken in the Senate chamber when Franken was sworn in on July 7, 2009.